AUGUST 6, 1897. ] 
the valency of the ion in that molecule and not 
upon the chemical nature of the ion. Under the 
influence of electric force, the ions in any mole- 
cule may be made to take up a new position 
while their center of mass remains fixed. If the 
force varies periodically, a part of the energy of 
the field is used in keeping up the oscillations 
of the ions about this center of gravity in the 
face of heat losses. Helmholtz applies Ham- 
ilton’s Principle to the equation of energy and 
arrives at results which correspond fairly well 
to observed facts. 
The whole book is written in delightfully 
simple language and seems to be quite free from 
typographical errors. We merely note, in pass- 
ing, that George Green held a fellowship in 
Cambridge from 1839 until his death in 1841, 
but never a professorship there. These lectures 
form one of a projected set of six volumes of 
Helmholtz’s Vorlesungen tiber Theoretische 
Physik which will be extremely useful to stu- 
dents of physics all over the world. 
HARVARD UNIVERSITY. B. O. PEIRCE. 
THE AMERICAN ASSOCIATION FOR THE AD- 
VANCEM ENT OF SCIENCE. 
GENERAL PROGRAM. 
THE regular meeting of the Council will be at 
the Hotel Cadillac (hotel headquarters ) at noon 
on August 7th. 
On Monday, August 9th, at 9 a. m., the 
Council will meet in the Council Room, Central 
High School. 
The first General Session of the Association 
will be held at 10 a. m., in the Auditorium of 
the Central High School. Owing to the death 
of Professor Edward D. Cope, the President of 
the Association, Professor Theodore Gill, of 
Washington, D. C., as Senior Vice-President, 
will call the meeting to order and introduce 
the President-elect, Professor Wolcott Gibbs, of 
Newport, R. I. Addresses of welcome will be 
made by his Honor Mayor William C. Maybury 
and Hon. Thomas W. Palmer, and President 
Gibbs will reply. Announcements by the Gen- 
eral, Permanent and Local Secretaries will then 
be made. 
The Addresses of the Vice-Presidents will be 
given in the afternoon as recorded below. In 
the evening Professor Theodore Gill, of Wash- 
SCIENCE. 
217 
ington, D. C., will give a memorial address 
on the life and work of the late President, Pro- 
fessor Edward D. Cope. Following this address 
there will be a reception given by the citizens 
of Detroit. 
On Tuesday, Wednesday, Thursday and Fri- 
day the regular meetings of the Council will be 
held at 9 a. m. and of the general session at 10 
a. m., followed in the mornings and afternoons 
by the meetings of the sections. 
On Friday morning officers will be elected 
and an agreement reached on the place of meet- 
ing for 1898, the fiftieth anniversary of the Asso- 
ciation. The concluding exercises and adjourn- 
ment of the sections of the Association and a 
social reunion and reception by the Ladies’ Re- 
ception Committee will take place in the evening. 
On Saturday there will be an excursion to 
Ste. Claire Flats. ; 
It is expected that the members of the Asso- 
ciation at Detroit will go in a body to Toronto to 
join in welcoming the members of the British As- 
sociation to America. For this purpose special 
rates will probably be secured by steamer and 
train from Detroit to Toronto. 
The programs of the sections are given below. 
These are as complete as possible up to the 
time of issue of this number of ScrENcE, but 
other papers will be presented at the meeting 
and entered on the daily programs. 
SECTION A.—MATHEMATICS AND ASTRONOMY. 
Address of the Vice-President: A Chapter in 
the History of Mathematics. By Professor W. 
W. Beman, University of Michigan, Ann Arbor, 
Mich. : 
1. A Problem in Substitution-groups. 
Dr. G. A. Miller, Ann Arbor, Mich. 
2, Continuous Groups of Spherical Transfor- 
mations in Space. By Professor H. B. Newson, 
Lawrence, Kans. 
3. The Treatment of Differential Equations 
by Approximate Methods. By Professor W. 
F. Durand, Ithaca, N. Y. 
4. Commutative Matrices. 
B. Shaw, Jacksonville, Tl. 
5. On the Theory of the Quadratic Equation. 
By Professor A. Macfarlane, Lehigh Univ., 
By 
By Professor J. 
, South Bethlehem, Pa. 
6. A New Principle in solving certain Linear 
